// run-pass fn iter_vec(v: Vec, mut f: F) where F: FnMut(&T) { for x in &v { f(x); } } pub fn main() { let v = vec![1, 2, 3, 4, 5]; let mut sum = 0; iter_vec(v.clone(), |i| { iter_vec(v.clone(), |j| { sum += *i * *j; }); }); println!("{}", sum); assert_eq!(sum, 225); }